The two principal carrier coatings for drawing rod are based on borax or lime. Lime carrier coatings have two main disadvantages. First, it is difficult to apply a lime coating since the lime floats in the water. Secondly, the lime coating flakes off lime particles in the work area causing disagreeable breathing conditions and dirty work areas.
Borax carrier coatings do not have the dusty flaking problem associated with lime coatings but borax carrier coatings suffer from the disadvantage that they pick up excessive moisture from the air during storage periods in the hot humid spring and summer weather. Excessive moisture from the air causes the borax coating to become soft and unuseable with the result that the coil must be sent back for recoating.
In addition to providing a carrier to pick up the drawing lubricant and carry it into the die the carrier coating should also be compatible with the wire processing steps following the drawing operation. If the wire is to be copper or tin coated then the carrier coating residue must be easily removed in a cleaning operation. If the wire is to be welded it is important that the carrier coating does not interfere with the welding operation. If the wire is for making nails then the carrier coating should not interfere with any wire cutting operation in the nail machine. Any lubricating qualities provided by the carrier coating is, of course, an added advantage.